Honda B2993 – Thermal Protector Circuit Short

Honda-specific code — factory diagnostic data

Last updated: May 6, 2026

Definition source: Honda factory description. Diagnostic guidance is based on factory-defined fault logic for this code.

B2993 sets when the climate control module sees the thermal protector signal pulled toward an unexpected voltage — typically shorted to ground or shorted to a power source. The module reads this as an invalid signal and disables the compressor as a safety precaution. The fault sits in either the protector element itself, its connector, or the harness run between the compressor and the module.

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B2993 Quick Answer

On a Honda, B2993 means the A/C compressor thermal protector circuit is shorted. The most common causes are water or oil contamination at the connector creating a low-resistance path, a chafed wire grounded against the compressor body or chassis, or an internally failed protector element. A/C cooling is disabled until the fault is repaired.

The Diagnostic Procedure

You will need a scan tool that reads Honda climate codes, a DVOM, the appropriate wiring diagram, and access to the A/C compressor. On hybrid models, follow the model-specific high-voltage shutdown procedure before disconnecting any compressor connector.

1. Confirm B2993 and capture freeze frame. Check for concurrent climate codes — shorts often involve liquid contamination that takes out multiple circuits at once.
2. Inspect the compressor connector for visible contamination. Refrigerant oil migration up the harness is a known Honda failure mode and creates conductive paths inside the connector.
3. With the system safe to disconnect (key off for conventional, full HV shutdown for hybrid), unplug the compressor connector. Inspect both halves for oil tracks, water staining, green corrosion, and damaged terminals.
4. Measure resistance across the thermal protector terminals at the compressor (connector unplugged from the harness). A healthy protector reads near short at room temperature. A reading of essentially zero ohms with no resistance variation may indicate the element is shorted internally — confirm against the model-specific spec.
5. Measure resistance from each thermal protector signal pin to the compressor body (ground). A short to ground in the harness or in the protector reads as low resistance here.
6. If the protector itself reads short to ground, replace the compressor — the protector is not separately serviceable.
7. If the protector is good, isolate the harness short. With the compressor unplugged and the climate module unplugged, measure resistance from each signal pin at the module connector to ground. A low reading confirms a harness short and points at where to look — typically a chafe-through point against the engine, transmission, or chassis.
8. Repair or replace the affected harness section. Do not splice in the engine bay area without proper heat-shrink and strain relief — repeat failures are common with poor splicing.
9. Clear B2993, run the A/C through a full cycle, and verify the code does not return.

Common Causes

• Water or oil contamination at the compressor connector: Most common single cause. Refrigerant oil migration creates a conductive path between pins or between a pin and ground. Inspect the connector at every service.
• Chafed signal wire grounded on chassis: The harness from the compressor runs through the engine bay where it can rub against engine components, brackets, or chassis seams. Insulation wears through and grounds the signal.
• Internally failed thermal protector: Less common but possible after a severe over-temperature event. The protector element is destroyed and the internal circuit shorts.
• Damaged or melted connector: A localised heat event (radiator fan failure, refrigerant leak ignition, exhaust shielding failure) melts the connector housing and creates pin-to-pin shorts.
• Climate control module fault: Rare. Confirm only after the protector and harness are proven good.

Severity & Driving

B2993 does not affect drivetrain operation. The engine starts, the brakes and steering work normally, and the hybrid system on hybrid models continues to operate. The A/C compressor is disabled by the module as a safety precaution, so you lose cooling. In hot weather this becomes a comfort and safety problem — extended driving without A/C in high temperatures fatigues the driver. On hybrid models the loss of A/C also reduces battery cooling capacity in hot weather. Repair before sustained warm-weather use.